FUNCTION: [Summary is not available for the mouse gene. This summary is for the human ortholog.] Spectrin is an actin crosslinking and molecular scaffold protein that links the plasma membrane to the actin cytoskeleton, and functions in the determination of cell shape, arrangement of transmembrane proteins, and organization of organelles. It is composed of two antiparallel dimers of alpha- and beta- subunits. This gene is one member of a family of beta-spectrin genes. The encoded protein localizes to the nuclear matrix, PML nuclear bodies, and cytoplasmic vesicles. A highly similar gene in the mouse is required for localization of specific membrane proteins in polarized regions of neurons. Multiple transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Jul 2008] PHENOTYPE: Homozygotes for spontaneous mutations exhibit tremors, progressive ataxia with hind limb paralysis, central deafness, reduced body weight, and shortened lifespan. Males are sterile, but females may breed. [provided by MGI curators]